PA6 and PET fibers, 0.5and 0.7mm, resp., defatted, soaked (0.5 h/40degreesC), washed, and buffered (pH 12), were treated 24 h38degreesC with 1 (or 2)% (fiber wt. basis) Pyrase or 1 % Alkalse, (alkaline proteases affecting peptide bonds), or 1 % of Greasex (enzyme hydrolyzing fatty acid triglycerides), then washed and dried I h/40degreesC. Adhesion to natural rubber, conventional and containing (2.5:10:1.5 w/w) 1,3-benzenediol-formaldehyde-silica as a proadhesive, showed Pyrase to be superior to Alkalse and the proadhesive to be inefficient Greasex reduced the adhesion. Argon plasma (50 or 100 W) feebled PA6, but improved adhesion of PET (by 65 and 70%, resp.). Oxygen plasma (50 or 100 IN) enhanced adhesion of PA6 (by 33 and 570/6) and PET (by 94 and 60016, resp.). 28 refs.